Enhancing Catalyst Lifetime of Bio-inspired Iron and Manganese Oxidation Catalysts: Advancing Green and Selective Oxidation Strategies in Organic Synthesis

Abstract

This thesis explores the development of bio-inspired iron and manganese complexes for catalytic oxidation reactions. Inspired by the function of non-heme enzymes, synthetic non-heme iron catalysts have been designed for the oxidation of C−H and C=C bonds using hydrogen peroxide as the oxidant. To enhance catalytic efficiency of the complexes, several ligand modification strategies have been investigated. Chapter 2 introduces non-heme iron complexes featuring bulky tri-isopropyl silyl (TIPS) groups as well as deuterium atoms in their ligand structures. These modifications significantly enhance catalytic activity, catalytic lifetime, and site-selectivity in both C–H and C=C bond oxidation. Beyond ligand deuteration, an alternative strategy was examined in Chapter 3 by developing a highly rigid quinoline-based ligand lacking benzylic methylene positions. This ligand was used to synthesize a novel iron complex, that showed enhanced efficiency and selectivity in epoxidation and dihydroxylation reactions of alkenes. Chapter 4 focuses on the synthesis of a ‘super bulky’ ligand system. Although an unexpected isomeric rearrangement did not lead to the formation of the intended ligand, this study provides valuable insights into ligand design and reaction pathways. Chapter 5 explores manganese-based complexes with electron-rich ligands for asymmetric epoxidation reactions. These complexes demonstrate high efficiency and enantioselectivity in the oxidation of styrenes and unsaturated carboxylic acid, achieving high turnover numbers and selectivities. The thesis concludes with an outlook on future research directions for molecular oxidation catalysts, emphasizing catalyst design, structural insights, and their applications in oxidation reactions.